Verapamil administration has resulted in occasional life threatening side effects related to its physiological actions. A number of less serious complaints have also been elicited in patients, but these "adverse effects" have rarely either limited the dosage of the drug which could be administered or prevented its continued use. A protocol was developed in order to determine the frequency, significance, and relationship to verapamil administration of these "adverse effects." Early results indicate that the drug appears to be well tolerated, but a few unsuspected potential side effects may have been uncovered.